(A) Recombinant AR LBD was tested for the binding affinity of the diterpenoids by measuring fluorescence polarization (mP) with an excitation wavelength of 470 nm and emission wavelength of 535 nm. Serial dilution was performed for the test compounds using synthetic androgen R1881 as a positive control. A representative plot from at least 3 independent assays is shown, and error bars represent the mean ± SEM. (B) CV1 cells transfected with 5XGAL4Luc reporter vector, VP16-AR-NTD, and GAL4DBD-AR-LBD (wild-type) were pre-treated for 1 hour with 10 µM of BIC, or T1, or T2, or T3, or vehicle (VEH), prior to the addition of 1 nM synthetic androgen R1881 for 24 hours. Error bars represent the mean ± SEM, n=5 independent experiments. Student’s t test: *p < 0.05; **p < 0.01; ***p < 0.001.